In order to ventilate a centrifugal pump (1) having a centrifugal pump outlet space (6) and a centrifugal pump suction space (4), as well as having an additional ventilation pump (3), preferably configured as a vacuum pump, having a ventilation pump inlet (14) and a ventilation pump outlet (15), which pump has a particularly simple structure and which can automatically ventilate itself, if necessary, without any complicate switching processes, it is proposed that both the ventilation pump inlet (14) and the ventilation pump outlet (15) are connected with the centrifugal pump outlet space (6) by way of a connection line (16, 17), in each instance, forming a secondary line.